From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753014AbcD1K31 (ORCPT ); Thu, 28 Apr 2016 06:29:27 -0400 Received: from terminus.zytor.com ([198.137.202.10]:47076 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752588AbcD1K3Z (ORCPT ); Thu, 28 Apr 2016 06:29:25 -0400 Date: Thu, 28 Apr 2016 03:28:46 -0700 From: tip-bot for Will Deacon Message-ID: Cc: hpa@zytor.com, tglx@linutronix.de, mingo@kernel.org, will.deacon@arm.com, paulmck@linux.vnet.ibm.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, peterz@infradead.org Reply-To: linux-kernel@vger.kernel.org, peterz@infradead.org, paulmck@linux.vnet.ibm.com, torvalds@linux-foundation.org, hpa@zytor.com, mingo@kernel.org, tglx@linutronix.de, will.deacon@arm.com In-Reply-To: <1461691328-5429-3-git-send-email-paulmck@linux.vnet.ibm.com> References: <1461691328-5429-3-git-send-email-paulmck@linux.vnet.ibm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/core] locking/Documentation: Clarify that ACQUIRE applies to loads, RELEASE applies to stores Git-Commit-ID: 3cfe2e8bc1cf74d78df6fe5ca3a1e1805472a004 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 3cfe2e8bc1cf74d78df6fe5ca3a1e1805472a004 Gitweb: http://git.kernel.org/tip/3cfe2e8bc1cf74d78df6fe5ca3a1e1805472a004 Author: Will Deacon AuthorDate: Tue, 26 Apr 2016 10:22:07 -0700 Committer: Ingo Molnar CommitDate: Thu, 28 Apr 2016 10:57:51 +0200 locking/Documentation: Clarify that ACQUIRE applies to loads, RELEASE applies to stores For compound atomics performing both a load and a store operation, make it clear that _acquire and _release variants refer only to the load and store portions of compound atomic. For example, xchg_acquire is an xchg operation where the load takes on ACQUIRE semantics. Signed-off-by: Will Deacon Signed-off-by: Paul E. McKenney Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: corbet@lwn.net Cc: dave@stgolabs.net Cc: dhowells@redhat.com Cc: linux-doc@vger.kernel.org Link: http://lkml.kernel.org/r/1461691328-5429-3-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- Documentation/memory-barriers.txt | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index 8b11e54..147ae8e 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -498,6 +498,11 @@ And a couple of implicit varieties: This means that ACQUIRE acts as a minimal "acquire" operation and RELEASE acts as a minimal "release" operation. +A subset of the atomic operations described in atomic_ops.txt have ACQUIRE +and RELEASE variants in addition to fully-ordered and relaxed (no barrier +semantics) definitions. For compound atomics performing both a load and a +store, ACQUIRE semantics apply only to the load and RELEASE semantics apply +only to the store portion of the operation. Memory barriers are only required where there's a possibility of interaction between two CPUs or between a CPU and a device. If it can be guaranteed that